The first international meeting on “Flavins and Flavoproteins” was held in Amsterdam in 1965. The list of speakers at this first symposium organized by Bill Slater and Cees Veeger included some of the most influential scientists in the field, such as Helmut Beinert, Vincent Massey, Tom Singer and Kunio Yagi, to mention only a few. Since then symposia were organized regularly every two to three years by members of the flavin community. Predating recombinant protein technology, research was confined to a handful of flavoproteins that could be obtained in sufficient amounts for detailed kinetic and mechanistic studies, i.e. Warburg’s Gelbes Ferment from yeast (later called Old Yellow Enzyme, OYE), D- and L-amino acid oxidase (from beef liver/kidney and snake venom, respectively), glucose and xanthine oxidase (from Aspergillus niger and milk, respectively). In the sixties and seventies, research focused on a better understanding of the chemical and physical properties of the flavin, or more precisely of the redox-active isoalloxazine ring, and its functions as a coenzyme of flavoproteins. When the first crystallographic structures of flavoproteins became available in the seventies, i.e. flavodoxin (FMN), glutathione reductase and p-hydroxybenzoate hydroxylase (both contain FAD) more specific questions concerning the interplay of amino acid residues and the flavin in the active site could be addressed. In the meantime, the protein database features more than 3700 structures of FMN or FAD-depending proteins enabling scientists to draw more general conclusions with regard to the structure-function relationships in flavoproteins. The advent of molecular biotechnology in the eighties boosted flavoprotein research in an unprecedented way: Instead of working with a few, hundreds of flavoproteins became accessible through recombinant gene expression and purification through affinity tags became child’s play compared to the time consuming protocols of the old days. Only a few years later the availability of entire genomic sequences provided insights into the extent and diversity of flavoproteins in bacteria, fungi, plants and animals. In addition to these developments, the last two decades have also witnessed new insights into the fascinating role of flavoproteins in photo- and magnetoreception, the participation in many biosynthetic pathways of natural products as well as the utilization of flavoenzymes in green chemistry (“biocatalysis”).